Electromagnetic clock



M. P. FAVRE-BULLE AND M. A. MOULIN. B-MJILMDULIN,NEECHENARD,GUARD\IAN0fM-0.AND M.A.A.MOUL|N.SOLE MINOR HEIRSOFSAID M.A.MOULIN,DEC'DELECTROMAGNETIC CLOCK.

APPLICATION FILED AUG.23, I920.

1,432,989. Patented Oct. 24, 1922.

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1 3 men/tom mm ubaln, Becki, 11181 g annual,

and M, P. Fayre -.B wLLe.,

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Awozzugy M. P. FAVRE-BULLE AND M. A. MOULIN.

mm. M.MOULIN, NEE'CHENAREGUARDIAN OF M. 0.AND M.A.A. MOULIN,SOLE MINORHEIRS OF SAID M.4A. MOUL|N,DEC'D ELECTROMAGNETIC CLOCK.

APPLICATION FILED AUG.23, I920. 1,432,989, Patented Oct. 24, 1922.

2 SHEETS-SHEET 2.

Patented Oct. 24, 1922.

UNITED STATES PATENT OFFICE.

MAURICE PHILIPPE FAVRE-BULLE, OF BOULOGNE, AND MARCEL ANDRE MOULIN,

DECEASED, LATE OF BFSANCON, FRANCE, BY BERTHA MARIE MARG-UERITE MOULIN,NEE CHENARD, OF PARIS, FRANCE, GUARDIAN OF MADELINE ODETTE MOULIN ANDMARIE ANNE ANDREE MOULIN, SOLE MINOR ANDRE MoULm.

HEIRS OF SAID MARCEL ELECTROMAGNETIC CLOCK.

Application and August as, 1920. Serial No. 405,434.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L,1313.)

To all whom it may concern:

Be it known that MAURICE PHILIPPE FAvnn-BULLn, acitizen of the FrenchRepublic, and residing at Boulogne, Seine, France, and MARCEL ANDRnMOULIN, deceased, late a citizen of the French Republic, and residing atBesancon, France (Mme. MARCEL ANDRI MoULIN, of Paris, France, guardianof MADELINE Onn'r'rn MOULIN and MARIE ANNE ANDREE MOULIN, minor heirs ofsaid MARCEL ANDRE MOULIN, legal representative), invented certain newand useful Electromagnetic Clocks (for which they filed application inFrance Dec. 23, 1918, No. 510,234, and in Great Britain Jan. 9, 1920),of which the following is a specifica tion.

This invention relates to electromagnetic clocks.

In electric clocks as constructed hitherto, in order to assure theconnection between the motion of the pendulum and the motion of thehands, the greater part of the devices employed in ordinar mechanicalclocks have been retained, w erein the regulating pendulum is actuatedby the actual toothed wheels driving the hands, and designers havealways sought to realize the conditions produced in this case byclockwork escapements that allow of imparting to the pendulum very shortimpulses close to the dead point.

In the case of a pendulum actuating the hands this condition isdifficult to execute, and it entails various drawbacks hereinafterreferred to. ()n the other hand it is insufficient to assure theisochronism of the oscillations of the pendulum, on account of thedisturbances caused by the retarding force due to driving the wholeconstituted by the devices for effecting the actuation of the hands.

The improvements forming the present invention relate to the combinationof a mechanical device for actuating the hands with an electromagneticdevice for maintaining the oscillations of the pendulum having a verygood efficiency, for allowing of compensating at each instant thepassive rc istanccs by an equivalent motive force in such a manner thatthe pendulum will behave just as if it were free.

The present improvements relate also to the mechanism which isdistinguished by a great simplicity of manufacture and which furtherallows of reducing the value of the retarding forces, and consequentlythe electric energy necessary for operating the clock.

Means are provided for assuring a good conservation of the electricbattery and of the automatic circuit breaker by making prolongedcontacts that allow of reducing the necessary current to a very lowvalue, and cutting off this current the moment when the counterelectro-motive induction force generated by the variations in themagnetic flux passing through the coil is a maximum.

This invention relates also to the improvements in the construction ofthe automatic circuit breaker of the pendulum and of the variousmechanical parts which have been designed for the purpose of a verycheap manufacture and very simple assembla e. It comprises also meansfor avoiding all risk of damage during transport of the clock, suchtransport being capable of being done without previously taking theclock to pieces and withoutany special precaution.

To enable the invention to be properly understood a practical embodimentthereof is described hereinafter by way of example with reference to theaccompanying drawings wherein:

Figure 1 is a front elevation partly in section of the generalarrangement of the clock. a

Figure 2 is a corresponding side elevation partly in section.

Figures 3 and 3 are detail views of the automatic interrupter foreffecting the successive closings of the circuit of the coil.

Figure 4 is a diagram of the'circuit and the electrical connections ofthe clock.

Figure 5 is a fragmentary perspective view of the magnetized bar andpendulum coil.

As shown in Figures 1 and 2, the clock comprises a pendulum of constantlength whose mass is constituted by the coil 1 attached by means of twowires 2 and 3, preferably of invar metal, to a rigid cross member 4 ofbrass.

The wires 2 and 3 form the sides of an isosceles tra ezoid so that thewhole shall be indeformab e by the weight of the coil 1 which assuresthe tension of the wires. The pendulum thus constructed is suspended toa support 5'by a silk thread 6 fixed by means of screws 7 and 8 whichare carried by the support 5 and afford a convenient means of regulatingthe length of the pendulum. The support 5 is fixed on a slab 9 of wood.or marble.

The coil 1 is traversed by a fixed magnetized bar 10 which has the sameS polarity at its ends and an intermediate N pole on its middle portion.This bar has the form of an arc of a circle and is fixed to the slab 9 bmeans of pillars 11 and 12.

o the cross member 4 of the pendulum there is fixed a stem 13 carrying aspring 14 serving as a pawl. At each oscillation of the pendulum in thedirection of the arrow F, Fig. 1, the pawl 14 causes the ratchet wheel15 mounted on the arbor 16 to turn through the width of one tooth. Thisarbor is journalled in two plates 17 and 18, stayed together by thepillars 19 and 20 which are held by the bracket 21 fixed to the slab 9of the clock. The mechanism for transmitting the rotational motion ofthe ratchet wheel 15 to that of the hands is character ized by a doublespeed-reducing gear consisting of a worm and worm wheel.

The arbor 16 of the ratchet wheel carries a worm 22 meshing with a wormwheel 23 carried by the intermediate arbor 24 (Figure 1).

This arbor 2-1 is journalled in angles 25 and 26 fixed to the plate 18.It carries a worm 27 meshing with a worm wheel 28 carried by the arbor29 of the minute hand.

At each return of the pendulum the pawl is raised, and the ratchet wheel15 is pre-' vented from moving back by the arresting spring 30 fixed ona pillar carried by the.

. plate 18.

The maintenance of the oscillations of the pendulum is effected by meansof an automatic interrupter operated by the pendulum itself,thusallowing of closing an electric circuit comprising the coil 1 and abattery P during a portion of the strokes of the E endulum in thedirection of the arrow F.

he passage of this current has the effect of generating anelectromagnetic force acting in the direction of the arrow F owing tothe presence of the magnetized bar 10 with consequent poles.

The automatic interrupter consists of parts which assure the driving ofthe mechanism for actuating the hands.

The electric circuit comprising the coil 1 and the battery P terminateson the one hand at the pawll4 and on the other hand at the ratchetwheel-1 5.

When the pendulum oscillates in the direction of the arrow F, contact ismade at the instant when the pawl. 14 touches the ratchet wheel 15 andcauses it to rotate. This pawl has the shape shown in the detail Figures3 and 3, and it is provided at its end with a' fibre block 31.:

As will be seen from Figure 3, contact when made remains only during aportion of the course of the pendulum in the direction of the arrow F.The said contact is then broken during the end of the said course andduring the return of the pendulum, because the insulating, fibre block31 is then rubbing over the tooth of the ratchet wheel.

The electric circuit connecting the interrupter thus constituted to thecoil land the battery P, is established by means of the wires 2 and 3suspending the said coil. This coil is constructed of a brass tube 32 tothe ends of which cheeks 33 and 34 are soldered or provided.

A cross member 35 fixed to these cheeks carries the parts 36 and 37 forattaching the wires 2 and 3. The part 37 is made of brass so that thewire 3 is connected to the mass. One of the ends of the solenoid ofinsulated thin wire wound around the tube 32 constituting the movablecoil 1. is likewise connected to the mass.

The tube 32 and likewise the cheeks 33 and 34 are split along ageneratrix of the cylinder so as to avoid the generation of oucaultcurrents due to the movement of the coil relatively to the magnet, whichcurrents would oppose the said movement.

The other end of the solenoid is insulated from the mass and isconnected to the end of the second suspension wire 2 attached to thecross member 35 and insulated from the latter by means of the part 36composed of bone or any other insulating material.

The upper end of the wire 2 is bent back so as to form a small loopclamped between the screw threaded stem 38 and the part 39 sliding in asquare hole in the insulating fibre sleeve 40 fixed to the cros member4. The attachment of the wire 2 to this cross member is effected bymeans of the nut 41 screwed upon the screwthreaded stem 38. The wire 2is kept stretched by the weight of the coil, and as is seen, it isinsulated from the cross member 4. The wire 3 isattached to this crossmember in a similar manner, but the sleeve 42 is of brass instead offibre, so that the wire 3 and the cross member are short-circuited. Thelength of the pendulum can be easily adjusted by screwing or unscrewingthe nuts 41 and 43.

The stem 13 upon which the pawl is fixed. is insulated from the crossmember 4 by matter of fact su'ilicient to approximate this condition,because the pendulum has a to assume a normal velocity for which themean value of the g force balances the mean value of the retardingforce.

As a matter of fact it this first value were greater than the secondvalue, the oscillations of the pendulum would have a tendency toincrease.

In these circumstances the velocity of the pendulum. at the instant whenit passes through the vertical would be greater, and c nsequently thecounter-electro-motivc inductive force would be higher.

The energy absorbed by the coil would diminish and consequently theelectromagnetic force would be weaker. n the other hand the value of theretarding force would be greater owing to the increase in velocity. Anormal velocity (regime) would not be long in being established for anamplitude very slightly greater than the initial amplitude, before adisturbance would be pro duced; The swing would be likewise very smallit the retarding force were to increase relatively to the driving force.

It will thus be seen that the arrangement employed for maintaining themotion of the pendulum allows of attaining a very great accuracynotwithstanding the slight varia tions that may occur in the value ofthe friction or of the electro-motive force of the battery, whereas inclocks o1 the same type as constructed hitherto the theo reticalconditions of isochro-nism are not satisfied owing to the infl .ence ofthe resisting effort which designers have not sought to make equal ateach instant to the driving force.

Thespecial magnet which is employed allows also of attaining a very goodutilination of the material whilst at the same time it can bemanufactured very cheaply. This magnet consists simply of a round bar ofsteel formed into the shape of an arc of 1: circle of a very largeradius of curvature. Permanent magnetization can be very easilypi'oduced by means of two solenoids arranged in series around the barand traversed in the reverse direction by a strong current in such amanner that the bar will have the same polarity at its ends and adifi'erent polarity in its middle. By this means the magnetic fluxemanating from the intermediate pole has a perfectly regular radialfield which is very intense in the region occupied by the coil at themoment of closing; the circuit.

Further, the position of the intermediate N pole made exactly such thatthe coil will embrace the said pole when the automatic interrupteris-closed, and when the latter is traversed by the maximum currentintensity. In these circumstances it will be perceived that each elementof current in the coil situated opposite the N pole is at right anglesto the lines of force, and'on the other hand the elements of currentsand the lines of force are contained in planes at right angles to theaxis of the magnet.

In these circumstances the electromagnetic forces due to the action ofthe elements of the current upon the magnet reach a maximum value.Moreover, since these forces are at right angles to the planescontaining the elementsof the current and the lines of force, they areall'di'rected along the axis of the coil, and their resultant reaches amaximum value in the sense that is favourable to the maintenance of themotion of the pendulum (Figure 4).

Consequently the theoretical conditions for the best utilization of themagnet and the coil are thereby realized.

In order to utilize the energy of the but tery under the best conditionsand to increasethe efficiency of the conversion of electric energy intomechanical energy, a contactis employed which is prolonged during aconsiderable portion of the course of the pendulum. Under theseconditions the electro-magnetic force that is required is very small,because it acts upon a considerable length of movement. Therefore thecoil can be madeof very strong wire, and the energy lost in the form ofheat can be reduced to a very small amount.

This arrangement is much more advantageous thanthe one employed inelectric clocks of the same type constructed hitherto wherein designershave attempted'to obtain very short current impulses because in thatcase itis necessary to have a considerable electromagnetic force as thedisplacement of this force is very small. Therefore, the intensity mustreach a'relatively high value and the result is that the heat developed.as a Joule effect which is proportional to the square of this intensity,is considerable and thus reduces the efliciency.

For the same reason it is diflicult to assure the maintenance of theinterrupter in proper working condition in the case of short currentimpulses, because it is necessary to break the circuitwhilst carryingrelatively high intensities with the result of producing considerablesparking. This drawback is remedied in our improved clock by employing alower intensity and in breaking the circuit carryingthis intensity,close to the dead point, that is to say, at the instant when thecounter-clectro-inotive inductive force is greatest, and consequentlythe. intensity has a minimum value. It will be perceived that thiscircuit-lnreaking takes place atthe mo ment when the conducting portionof the pawlv it ceases to drive the ratchet wheel (Figure 9,). percehedthat the circuit-breaking takes ()n the other hand it will be place at apart of the tooth of the ratchet wheel which is different from the partat which contact has been made.

By this-means the contact surfaces are thoroughly cleaned and contactremains in a good condition indefinitely. This last feature allows ofobtaining perfect results even without having recourse to the use, forthe purpose of contact, of cappings of precious metals, such as areemployed in the majority of electric clocks.

The mechanical apparatus for actuating the hands has been designed toreduce to a minimum the mechanical energy required for maintainin themotion of the pendulum. This resu t is achieved by the use of amechanism of very small size for reducing the motion, which in similarclocks is usually done by means of a series of wheels and pinionssimilar to the wheel-work employed in clocks driven by weights orsprings. The ratchet wheel 15 has very few teeth andit has a very smalldiameter as have also the worm wheels and worm in order to reduce themoments of inertia to a minimum. Under these conditions the retardingforce due to the inertia of these parts when they are started is verysmall. This resistance is also utilized to effect the pressure of theelectric contact assured by the pawl 14 and the ratchet wheel 15, whichcontact does not add any supplementary effort, or consume any additionalpower.

On the return of the pendulum the friction of the nose of the pawl takesplace on the fibre block 31, thereby reducing the coeflicient otffriction.

The diminution of the necessary force and the use of a coil of highresistant wire allows also of reducing considerably the wear of thebattery. Consequently batteries may be employed made like the standardsof electromotive force, thereby allowing of obtaining a constancy of thevoltage which is very diflicultly attained in the case of a high rate rof discharge as in electric clocks hitherto constructed. This propert isvery important in the case of pen ulums of small length when it isdesired to get amplitudes for which isochronism is no longer strictlyrequired.

The diminution of the intensity of the current passing through the coilis likewise very favourable to a good preservation of the magnet.

The costs of manufacture of the improved pendulum are incomparably lowerthan the cost of manufacture of electric clocks of the same typehitherto constructed owing to the very small number of arts that areemployed, the majorit of whic serve to perform a number of differentfunctions. For instance the wei ht or mass of the pendulum isconstituted by the actual coil 1.

The rigid pendulum that is ordinarily employed is replaced by a singlemass suspended by two metal wires whose length may be adjusted inassembling the clock in a very easy manner by means of the nuts 41 and43; said wires being also utilized for supplying current to the movablecoil. The improved construction of the pendulum allows of approximatingto the conditions of a simple pendulum and thus obtaining a maximummoment of inertia for a given mass of the pendulum. The apparatus forcontrolling the speed-reducing mechanism actuating the hands and theautomatic interrupter are constituted by the same parts. Thespeed-reduction is effected by means of a mechanism which is much lessextensive than those employed in ordinary mechanical clocks.

he very small bulk of this mechanism allows of reducing considerably thedimensions of the frame of the clock.

The improved general arrangement has further the great advantage ofenabling the clock to be extremely easily transported without previousremoval of the pendulum, and without any special precaution. As a matterof fact the weight mass of the pendulum constituted by the coil 1 isheld perfectly by the fixed mangnet 10 which extends through it, and itis sufficient to fix it upon the latter in order to render the clockcapable of being turned upside down or in anIyIway without risk ofdamaging any part.

aving now described our invention, what we claim as new and desire tosecure by Letters Patent is 1. In electromagnetic clocks the combinationwith a mechanical apparatus for actuating the hands of anelectromagnetic apparatus for keeping up the oscillations of thependulum which allows of compensating at each instant the passiveresistances by an equivalent driving force, in such a manner that thependulum behaves as if it were free.

2. In electromagnetic clocks, a magnetized bar having consequent poles,and a movable coil adapted to traverse said magnetized bar.

3. In electromagnetic clocks a movable coil adapted to be traversed byan intermittent current, a magnetized bar having consequent oles whichextend through the said coil, sai magnetized bar being curved andmagnetized in such a manner that the coil surrounds the intermediatepole at the in stant when the intensity of the current passing throughthe same is a maximum.

4. In electromagnetic clocks an electromagnetically actuated pendulum,an electric circuit including the elebtro-magnetically actuatedpendulum, and circuit-interrupting means operating to maintain thecircuit closed for a long period starting before the pendulum reachesits vertical position, and lasting until the pendulum is close up tosaid osition, for the purpose of diminishing t e mean intensity of therequisite current and cuttin ofl said current at the moment when it is aminimum owing to the counter-electromotive inductive force, which latteris a maximum at the same time as the speed of movement of the coil.

5. In electromagnetic clocks effecting the control of the mechanismactuating the hands and the periodic closings and openings of theelectric current circuit by means of the same parts comprising apendulum, a pawl fixed to the pendulum, a ratchet wheel adapted to drivea hand-actuating mechanism; the ratchet wheel and pawl being made ofelectrical conducting material and adapted to be connected with anelectric circuit, and an insulating member carried by the pawl movableover the ratchet wheel at the instant of the return of the pawl.

6. In electro-magnetic clocks, an electromagnetic coil constituting apendulum, spaced suspending members on said coil having electricalconnection therewith, and a clock hand actuating mechanism locatedbetween said suspending members.

7. In electromagnetic clocks, a pendulum whose mass is constitutedsolely by a movable coil attached by means of two metal wires,preferably of invar metal, to two transverse rigid parts one of which iscarried by the coil and the other is fixed to a suitable suspensiondevice.

8. In electromagnetic clocks a coil, wires for suspending the coil, inthe form of independent electrical conductors for assuring theconnections of the said coil and adjustable attaching means for thewires facilitating the regulation of their length.

9. In an electro-magnetic clock, a clock hand actuating mechanism, apendulum, electro-magnetic actuating means for the pendulum, anelectrical circuit including said electro-magnetic actuating means, apawl actuated by the pendulum to intermittently engage and actuate thehand actuating mechanism incident to a swinging movement of thependulum, and circuit interrupting means included in said circuitoperating to close the latter at the precise instant at which resistanceto the movement of the pendulum occurs due to the driving coaction ofthe pawl with the hand actuating mechanism.

In testimony whereof we have signed our names to this specification.

MAURICE PHILIPPE FAV'RE-BULLE.

v". MARCEL ANDRE mouuu.

